Day 22

The asteroid Vesta, as seen by the Dawn space probe. Vesta is the second largest asteroid in the Solar System. [Credit: NASA, JPL-Caltech, UCLA, MPS, DLR, IDA]

“Asteroid” is a general term for a lot of small bodies in the Solar System, from chunks of rock and rubble up to substantial, very planet-like objects. The second category includes Vesta, recently visited and studied by the Dawn spacecraft. Vesta has sort of a squashed shape, more like a bread roll than a sphere, but Dawn’s measurement of its gravity shows that the asteroid has a differentiated interior: a core, mantle, and crust, much like Earth, the Moon, and the other rocky planets. Vesta even has traces of water, a result that is growing less newsworthy with each discovery that water is incredibly common in the Solar System.

Possibly the most famous asteroid, though, isn’t a real object. It’s the asteroid B-612, the dwelling place of the Little Prince in the mystical children’s book by French aviator Antoine de Saint-Exupéry. (OK, maybe the asteroids in TheEmpire Strikes Back are more famous, but none of them were named in the movie.) For my birthday in 2012, I wrote a little post about the science of the Little Prince’s asteroid, and just learned last week that the essay won a spot in the Open Lab anthology of the best science writing online!

Asteroid B-612 also gave its name to the B612 Foundation, an organization dedicated to finding asteroids that are potentially dangerous to Earth. While there’s no cause to panic, we know that big chunks of space rock have hit Earth in the past, and will do so again in the future. Locating and tracking asteroids that could possibly prove risky is an important job, one which we all should support.

Real asteroids may not be as poetic as B-612, but they are nevertheless beautiful objects in their way. We know there are billions of planets in the Milky Way, and studying asteroids is one way we can learn how those planets — including ours — came to be.